In the past, a rotary compressor, as disclosed for example in Japanese patent document No. JP-A-H06-288358, has been known in the art. This rotary compressor is equipped with a cylinder and a piston member which is rotated eccentrically. The cylinder and the piston member together define a compression chamber which is a closed space. In addition, the cylinder and the piston member are provided with end walls. The end wall of the cylinder and the end wall of the piston member face each other across the compression chamber. And, the rotary compressor causes the piston member to rotate eccentrically to thereby compress fluid drawn in to the compression chamber.
In the rotary compressor, the internal pressure of the compression chamber is applied to both of the end wall of the cylinder and the end wall of the piston member. Upon compression of the fluid in the compression chamber, the internal pressure of the compression chamber becomes higher. Consequently, if no countermeasures are taken, the cylinder and the piston member will be moved in opposite directions away from each other by the pressure applied to each of the end walls. As a result, the gas-tightness of the compression chamber is no longer maintained, thereby causing a drop in the efficiency of compression.
Therefore, in the rotary compressor disclosed in the aforesaid patent document, pushing force is applied to the end wall of the piston member to avoid expansion of the clearance between the piston member and the cylinder, thereby ensuring the gas-tightness of the compression chamber.